import org.junit.Test;

import java.text.SimpleDateFormat;
import java.time.LocalDate;
import java.time.format.DateTimeFormatter;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;

/**
 * 传统多线程存在线程安全问题
 */
public class TestSimpleDateFormat {
    public static void main(String[] args) throws Exception{
        DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyyMMdd");
        Callable<LocalDate> task = new Callable<LocalDate>() {
            @Override
            public LocalDate call() throws Exception {
                return LocalDate.parse("20161218", dtf);
            }
        };
        ExecutorService pool = Executors.newFixedThreadPool(10);
        List<Future<LocalDate>> results = new ArrayList<>();

        for (int i = 0; i < 10; i++) {
            results.add(pool.submit(task));
        }
        for (Future<LocalDate> future : results) {
            System.out.println(future.get());
        }

        pool.shutdown();
    }

    /**
     * java1.8以前的api
     * @throws Exception
     */
    @Test
    public static void test1() throws Exception{
        SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd");
        Callable<Date> task = new Callable<Date>() {
            @Override
            public Date call() throws Exception {
//                return sdf.parse("20161218");   // 抛出异常
                return DateFormatThreadLocal.convert("20161218");   // 线程安全的
            }
        };
        ExecutorService pool = Executors.newFixedThreadPool(10);
        List<Future<Date>> results = new ArrayList<>();

        for (int i = 0; i < 10; i++) {
            results.add(pool.submit(task));
        }
        for (Future<Date> future : results) {
            System.out.println(future.get());
        }

        pool.shutdown();
    }
}
